Listeria challenge testing

From March 2011 newsletter

We have recently investigated a novel approach to Listeria challenge
testing to see if it would give similar results to the standard more
complex methods.

Microbiological challenge tests are essential for assessing the
potential for growth of specific foodborne pathogens or spoilage
microorganisms in a food product from point of manufacture
through to consumption. This involves the inoculation of a product
with relevant microorganism(s) and storing under controlled
environmental conditions in order to assess the risk of food
poisoning or to establish product stability.

Product safety and stability

The use of challenge testing to assess product safety and stability
has increased over the past few years, particularly with respect to
food pathogens such as Listeria monocytogenes, where evidence is
required to demonstrate the potential for growth of this organism
throughout life. However, existing recommended procedures are
often complex.

New approach

We explored the new approach with a pre-packed sliced ham
product. Results showed that a single storage temperature could
be used and that a lower temperature could be included in
challenge test protocols if this could be maintained throughout part
of the manufacture and distribution chain. The need to adapt the
cultures by growing under chilled conditions prior to inoculation
was also shown to be unncessary.